Flow deformation press



Oct. 13, 1964 Filed April 28, 1961.

K. GRIESINGER FLOW DEFORMATION PRESS 2 Sheets-Sheet 1 Oct. 13, 1964 Filed April 28, 1961 K. GRIESINGER 3,152,696

FLOW DEFORMATION PRESS 2 Sheets-Sheet 2 INVENTOR MM! WQ AW B Y m4 M/ fl Mz? ATTORNEY;

United States Patent 3,152,696 FLOW DEFORMATION PRESS Karl Griesinger, Jebenhausen, Wurttemberg, Germany,

assignor to L. Schuler AG, Goppingen, Wurttemberg,

Germany Filed Apr. 28, 1961, Ser. No. 106,388 Claims priority, application Germany May 4, 1960 9 Claims. (Cl. 2071) The invention relates to a flow deformation press.

In known flow deformation presses the ram is operated either by a toggle joint or directly by a crank. If the ram is driven by a toggle joint the impact velocity of the punch on the blank contained in the die is relatively low. This is an advantage because it lessens the shocks to which the press is exposed. Moreover, it is held that a relatively slow impact velocity of the punch on the blank favorably affects the ensuing flow deformation of the material. a

However, a disadvantage of a toggle joint press is that in the vicinity of its forward or working dead centre .the speed of the ram is very slow so that the descent of the punch into the die and its withdrawal therefrom occupies a relatively long period of time, whereas the speed in the neighborhood of the rearward dead centre is high and the change in the direction of motion of the ram is correspondingly rapid.

Now, the work must be stripped from the punch and a fresh blank loaded into the die during this latter working phase of the ram during which the punch is a certain minimum distance away from the die. Generally the duration of this working phase during which the work can be stripped from the punch and a fresh blank loaded into the die is about /3 of the total duration of each working cycle. The number of down strokes which can .be performed on such a press is therefore generally limited by the fact that sufficient time must be available for stripping the work and for introducing the fresh blank into the die.

In other known types of flow deformation press in which the ram is directly driven by a crank or by an eccentric the variation of the angularity of the ram and of its speed is represented by a sine function. In such presses the angular range within which pressing is actually performed is not more than about 30, and a crank motion through an angle of 300 is available for loading the blank and for stripping the pressing. Thus the period which can be utilized for loading the blank and for stripping the pressing may be as much as Vs of the total cycle of reciprocation.

In such presses the time in each Working cycle available for introducing the blank and for stripping the pressing is therefore much longer and the rate of reciprocation of such presses is not therefore limited by the time available for loading and stripping but rather by the fact that the punch must not strike the blank in the die at too high a speed and thereby subject the press to excessive shock loads as the rate of reciprocation is increased.

The rate of reciprocation of known flow deformation presses cannot therefore be substantially raised beyond certainlimits. Flow deformation presses operated by the above mentioned known types of drive means are usually run at a rate of 60 working strokes per minute and only in very special circumstances, depending upon the nature of the pressed material and the kind of pressing required, have toggle joint presses reached operational speeds up to 100 strokes per minute. These rates cannot, however, be achieved by known presses when dealing with standard aluminium blanks.

In a known type of flow deformation press a drawbar leading to the ram is attached to a crank which oscillates "ice about its forward dead centre position, remote from the ram. These oscillations are produced by a revolving crank of smaller throw in that a connecting rod attached to the crank pin of the revolving crank is directly connected with the crank pin of the oscillating crank which works the drawbar (connecting rod). If there is to be an optimum distribution of forces in this form of construction the axis of revolution of the rotating crank must be so disposed that its connecting rod works approximately at right angles to the oscillating crank when the latter is in the vicinity of its dead centre between working strokes.

This, however means that the crankshaft of the rotating crank would have to be so located that the plane defined by this shaft and the axis of the oscillating crankshaft were roughly perpendicular to the plane defined by said axis and the guide means of the ram, a necessity which is not always an advantage from the point of view of other structural requirements. Since in this known press the crank oscillates merely about its forward dead centre position the associated drawbar must be longer by twice the throw of the oscillating crank than would be the case if the rearward dead centre of the oscillating crank were utilized for the idle motion between working strokes.

Moreover, in this known press the entire tool assembly must be accommodated between the ram and the shaft of the oscillating crank and the drawbar attached to the ram must therefore be lengthened by a further substantial amount beyond what would be otherwise necessary.

In this known press the drawbar is thus of very great length. This is a drawback because of the natural elasticity inherent in a member of great length and in view of the fact that there is a steep rise in specific pressure when pressing a part by flow deformation.

The invention therefore proposes to provide a second crank on the Working crankshaft at an angle to the working crank, the connecting rod of the rotating crank being pivotally attached to this second crank, and to construct the connecting rod between the working crank and the ram as a compression-stressed member.

It is a special advantage of this proposal that whilst providing optimum conditions for the driving mechanism, the designer is free to locate the rotating crank nearly anywhere in the press frame, because by suitably choosing the relative angle between the working crank and the second crank on the working shaft he can always arrange for the angle of application of the connecting rod of the rotating crank to be substantially at right angles to the second crank when the working crank is in dead centre position. Furthermore, it is also open to the designer to control the existing conditions of force transmission by varying the throw of the working crank in relation to the throw of the second crank on the same shaft.

As a result of these possibilities a flow deformation press operating at an angle of 45 can be designed in which the rotating crank is located below the tool assembly, an arrangement which gives rise to a particularly favorable and compact form of construction. Moreover, in such an arrangement the working crank can be designed to oscillate about its forward dead centre, nearest the tool assembly, without the consequent necessity of locating the rotating crank in a region which is restricted by the presence of the tool assembly and the position of this dead centre.

In an upright flow deformation press, for instance, it would be impossible to accommodate this rotating crank and the clutch which is preferably located on the same shaft so far up. The press proposed by the invention shares the advantage of known toggle joint presses of permitting the connecting rod between the working crank and the ram to be embodied in a compression member. However, the proposed press has the advantage over 3 toggle joint presses of permitting this compression member to be very much shorter than in toggle joint presses because the necessity inherent in the latter of locating the rotating crank as closely as possible below the toggle joint, and hence in the region between the tool assembly and the fulcrum of the rear toggle lever, does not arise.

In the previously mentioned press which operates near the rearward dead centre, remote from the tools, the drawbar from the working crank to the ram was necessarily of considerable length. In order to keep the clasticity of such a long drawbar Within tolerable limits this drawbar had to have a considerable cross section. The mass of such a drawbar was therefore too great to permit a more or less economic source of power for driving such a press to achieve high rates of reciprocation in view of the great inertia of the masses that had to be accelerated. On the other hand, a ram embodied in a compression member can be extremely short with a small mass and thus offers the necessary conditions for a considerable increase in the rate of reciprocation that can be achieved.

For these reasons the use of a drawbar as a connecting rod is out of the question in flow deformation presses which are intended to operate at a rate of reciprocation which substantially exceeds that of known flow deformation presses.

For guiding the ram, accommodating the drive means and the mass of the tools, the cross sections of the walls of the frame of flow deformation presses are necessarily always fairly substantial. These considerable cross sections elongate only little when subjected to the loads due to pressing, even if the frame is fairly long. However, these masses need not be accelerated, contrary to what is the case in the known aforementioned press provided with a drawbar. It is therefore not a matter of importance that a connecting rod in the form of a compression member throws the load on the casing.

In the press proposed by the present invention it is also a considerable advantage that the series association of two linked crank motions permits the speed of motion of the ram along its path to be suitably controlled to provide a much longer time for stripping the pressing than is available in toggle joint presses, and that the speed of the ram when contacting the blank can be reduced below the impact velocity obtaining in these toggle joint presses.

In the case of an eccentric drive the applicants have already proposed to attach the connecting rod pivotally to the driving eccentric with the interposition of a supplementary eccentric mounted within the driving eccentric itself. This supplementary eccentric has drive means of its own so that the resultant compound motion is a combination of two sine functions. However, this drive does not provide optimum conditions for a flow deformation press, because in a flow deformation press the length of the working range of the stroke of the ram is less than mm. and after adding the distance required for the punch to clear the feed means for the blanks, 30 to 40 mm.

In view of these distances it is immaterial whether or not the idle part of the stroke is performed at a higher speed. On the other hand, the individual cranks in the proposed press are mounted in stationary bearings in the frame of the press. The first crank rotates through full revolutions of 360", whereas the second crankshaft merely oscillates on its axis. The ratio of the throw of the second crank and the throw of the ram driving crank on the same crankshaft determines the power transmission ratio as well as the speed ratio, whereas any variation of the angle between the dead centre positions of the two cranks permits the functional relationship between time and distance travelled by the ram to be varied. The throw of the rotating crank determines the angle of oscillation of the second crankshaft and hence determines the particular portion of the sine motion which is utilized and itself modified by a trigonometric function. The timemotion diagrams which can be generated by the proposed drive means are particularly suitable for flow deformation presses.

In one embodiment of the invention the throw of the second crank is about 1 /2 times the throw of the rotating crank. ,Moreover, the throw of the driving crank for the ram is about twice that of the revolving crank.

This embodiment of the invention may be further developed by making the length of the connecting rod bebetween the two cranks equal to the distance between the axis of the two crankshafts so that these two cranks simultaneously pass through the positions in which they are in quadrature to their dead centres. This is, however, by no means a necessity. When the rotating crank is in dead centre position, the second crank must, however, be a suitable distance away from its dead centre position.

The driving crank for the ram in one embodiment of the invention is placed at an angle to the second crank on the same shaft in such manner that the dead centre positions of both cranks are separated by an angle between 40 and 60.

In order to ensure that the thrust acting on the cranks in drive means according to the invention is transmitted in optimum manner, at least the crankshaft which carries the driving crank for the ram is supported not only by its axle pins but also by bearings which support the peripheries of the webs of the crank.

Other features of the invention will emerge as the following more particular description of the accompanying drawings proceeds, and they will form the subject matter of claims. Individual features may be severally or jointly incorporated in embodiments of the invention.

The drawings illustrate one constructional form of the invention, in which FIG. 1 is a longitudinal section of the parts necessary for an understanding of the invention;

FIG. 2 is a section taken on the line IIH in FIG. 1;

FIG. 3 is a motion diagram representing the positions of the ram as a function of time;

FIG. 4 shows an alternative embodiment in a longitudinal sectional view coplanar with that of FIG. 1.

In the embodiment of the invention illustrated in FIGS. 1 and 2, a mainshaft 1 of the press carries a crank 2 with a crankpin 3 which is linked by a connecting rod 4 with a crank pin 5 on a crank 6 keyed to a crankshaft 7. This crankshaft 7 carries a further crank for reciprocating a ram 8 which is slidably displaceable in the press frame, said crank being formed by two webs 9 and '10 and a crankpin 11 (see FIG. 2) upon which is mounted the big end of a connecting rod 12 of which the small end is pivotally attached to the ram 8. The crankshaft 7 which carries the crank assembly 9, 10, 11 for driving the ram 8 is supported not only by its two axle pins 13 which are mounted in a frame 14 of the press but also by bearings 15 under the crank-arms at their ends remote from the crankpin 11.

Other views of the inventive flow deformation press appear in applicants copending patent application Ser. No. 106,387 filed on even date herewith. Only those details have been described herein which are necessary for the understanding of the present invention.

FIG. 3 is a curve showing the relation between time and distance of travel of ram 8.

The time is plotted on the abscissa 16 and the distance of travel of ram 8 on the ordinate 17. Curve 18 is a sine function representing the motion of the ram 8 in a conventional crank press. Curve 19 represents the motion of the ram in a press as herein described. In this press the throw of crank 5, 6 is a little over 1% times the throw of the rotating crank 2, 3. Consequently crankshaft 7 will oscillate through an angle of about The throw of crank assembly 9, 10, 11 for reciprocating the ram 8 is about of the throw of crank 5, 6.

The dead centre positions of the driving crank 9, 10, 11 for the ram 8 and of crank 5, 6 are angularly displaced by about 45. The diagram in FIG. 3 includes a straight line 20 at a distance above the abscissa representing the actual working stroke of the punch after entering the die, that is to say the distance of travel of the punch whilst pressing the blank. i i

The slopes of tangents 21 and 22 at the points of intersection of curves 18 and 19 with this straight line represent the speeds at which the punch makes contact with the blank in the case of a conventional crank press (curve 18) and in drive means constructed as proposed by the present invention (curve 19), respectively. It will be seen that the speed of impact of the punch on the blank when driven in the manner proposed by the invention is substantially less than the speed of impact in a conventional crank press.

In the special embodiment of the invention based on the aforementioned design data the impact velocity of the punch on the blank is in fact less than in the case of a pure toggle joint drive. This follows from a math matical evaluation of the function describing the motion of a toggle joint press and that describing the motion generated by the drive means according to the invention.

In the region between the straight line 20 and the abscissa 16, dot-dash curve 23, representing the motion generated by a pure toggle joint drive, rises approximately midway between the two curves 18 and 19 but intersects curve 19 within the lower third of its full elevation because the slope of this section of curve 19 is steeper than that representing the toggle drive motion.

The distance of the straight line 20 above the abscissa corresponds approximately to a punch pressing stroke of 6 mm. into the die. The total stroke in this curve is assumed to be a little over 150 mm. Before the pressing can be stripped and a fresh blank placed into the die the punch must be retracted not only by the length of its pressing stroke but a sufficient additional distance to clear the feed members for loading the blank into the die. The punch must therefore generally be withdrawn a minimum distance of 40 mm. from its working or forward dead centre before the blank feeding and stripping operations for removing the pressing can begin.

In the embodiment illustrated the drive has been deliberately designed to ensure that when reaching this point after having passed through the working dead centre the velocity of the punch will already exceed that generated by a pure toggle joint drive and that curve 19 at this point will have already crossed the curve 23 representing the pure toggle joint drive. In the illustrated example this means that the drive according to the invention generates an impart velocity on the blank which is even less than the impact velocity in the case of a pure toggle joint drive and that, furthermore, the feeding of the fresh blank and the stripping of the work can begin at an earlier stage than in a pure toggle joint drive.

In the embodiment shown in FIGS. 1 and 2 the drive means are so designed that the driving crank assembly 9, 7, 11 for the ram 8 which performs an oscillating to and fro motion is in dead centre position in relation to the axis of ram 8 when the punch exerts its ultimate pressure upon approaching its full depth of descent into the die. This is particularly advantageous because the very high ultimate pressure does not then react on the drive means but is taken up by the crank bearings, particularly by the bearings which support the rear peripheral edges of the Webs of the crank. However, other forms of construction are feasible in which the crank in its final position is only approximately in dead centre position or even relatively far away from dead centre position. If this is the case a part of the final pressure must be taken up by the drive means.

The two cranks 9, 10, 11 and 6 could be replaced by a triangular plate or phasor 16 shown in the alternative embodiment illustrated in FIG. 4. One corner of said triangular plate would then be pivoted in the frame of the press about shaft 7 in the same way as the two crank arms x 6 9 and 10. The second corner of the triangular plate would carry the crankpin 11 for connecting rod 12 whereas crankpin 5 would be mounted in the third corner for connecting rod 4. In this arrangement in which the cranks corresponding to cranks 10, 9, 11 and 6 would all be coplanar, being all contained in the plane of the triangular phasor plate 16, the section of the crankshaft 7 between crank-arm 6 and crank-arm 10 shown in FIG. 2 would not be subjected to torsional load.

What I claim is:

1. In a flow deformation press having a ram reciprocable between a forward and a rearward dead centre position, the improvement comprising, in combination, a driving shaft rotatable at a uniform velocity, a driven shaft substantially parallel to said driving shaft and adapted to perform a limited oscillatory movement, a first crank rigid with said driving shaft and a second crank rigid with said driven shaft, a crankpin for each of said cranks, the distance between said driven shaft and the associated crankpin being larger than that between said driving shaft and the associated crankpin, a connecting member pivotally linked to said crankpins for oscillating said second crank about its dead centre upon rotary motion of said first crank, and a compression-stressed pressing rod eccentrically linked at one end to said driven shaft and pivoted at the other end to said ram, a crankpin for said eccentric link between said pressing rod and said driven shaft angularly displaced on said driven shaft with respect to the crankpin of said second crank, the distance between said driven shaft and said crankpin of the eccentric link being larger than that between said driven shaft and the associated crankpin, whereby the velocity of said ram will be higher while moving from said forward to said rearward dead centre position and lower while moving in the opposite direction.

2. In a press, the combination according to claim 1, wherein said distance between said driven shaft and the associated crankpin has a proportion of substantially 1 /2 to 1 with respect to said distance between said driving shaft and the associated crankpin.

3. In a press, the combination according to claim 1, wherein said distance between said driven shaft and said crankpin of the eccentric link has a proportion of substantially 2 to 1 with respect to said distance between said driving shaft and the associated crankpin.

4. In a press, the combination according to claim 1, wherein said connecting member has an operative length equal to the linear distance of said driving and said driven shafts, so that said cranks simultaneously pass through positions in which they are in quadrature with their relative dead centre positions.

5. In a press, the combination according to claim 1, wherein said angular displacement between said eccentric link and said crankpin of the second crank is selected with a value so that the angular displacement of the relative dead centre positions is within the range of 40 to 60 degrees.

6. In a press, the combination according to claim 1, wherein said eccentric link has a pair of crank webs flanking the eccentric portion, at least said crank webs being supported by additional bearings so as to compensate for axial stresses.

7. In a press, the combination according to claim 1, wherein the angular position of said eccentric link with respect to said driven shaft is selected with a value whereby said crankpin of the eccentric link is substantially in its dead centre position when said ram applies its ultimate pressure toward the end of its path to said forward dead centre position.

8. In a press, the combination according to claim 1, wherein said second crank is coplanar with said eccentric link, further comprising substantially triangular phasor means accommodating said crankpins of the second crank and of the eccentric link, one corner of said phasor means being adapted to oscillate about said driven shaft while 7 8 the other corners are respectively articulated to said press- 1,872,242 Byerlein Aug. 16, 1932 ing rod and to said connecting member. 2,560,250 Roucka et a1 July 10, 1951 9. In a press, the combination according to claim 1, FOREIGN PATENTS wherein the path of reciprocation of said ram has an angle of substantially 45 degrees with respect to the line 5 753:246 France g- 1933 connecting said driving and said driven shafts. 107,215 Great Brltaln June 8, 1917 OTHER REFERENCES e erences Clted m the file of t 15 Pa en Mechanlsms and Dynamics of Machinery, by Mabie UNITED STATES PATENTS and Ocvirk, published by Wiley & Sons: New York, 1957.

425,971 Baird Apr. 22, 1890 10 (Pages 1626 relied upon.) 

1. IN A FLOW DEFORMATION PRESS HAVING A RAM RECIPROCABLE BETWEEN A FORWARD AND A REARWARD DEAD CENTRE POSITION, THE IMPROVEMENT COMPRISING, IN COMBINATION, A DRIVING SHAFT ROTATABLE AT A UNIFORM VELOCITY, A DRIVEN SHAFT SUBSTANTIALLY PARALLEL TO SAID DRIVING SHAFT AND ADAPTED TO PERFORM A LIMITED OSCILLATORY MOVEMENT, A FIRST CRANK RIGID WITH SAID DRIVING SHAFT AND A SECOND CRANK RIGID WITH SAID DRIVEN SHAFT, A CRANKPIN FOR EACH OF SAID CRANKS, THE DISTANCE BETWEEN SAID DRIVEN SHAFT AND THE ASSOCIATED CRANKPIN BEING LARGER THAN THAT BETWEEN SAID DRIVING SHAFT AND THE ASSOCIATED CRANKPIN, A CONNECTING MEMBER PIVOTALLY LINKED TO SAID CRANKPINS FOR OSCILLATING SAID SECOND CRANK ABOUT ITS DEAD CENTRE UPON ROTARY MOTION OF SAID FIRST CRANK, AND A COMPRESSION-STRESSED PRESSING ROD ECCENTRICALLY LINKED AT ONE END TO SAID DRIVEN SHAFT AND PIVOTED AT THE OTHER END OF SAID RAM, A CRANKPIN FOR SAID ECCENTRIC LINK BETWEEN SAID PRESSING ROD AND SAID DRIVEN SHAFT ANGULARLY DISPLACED ON SAID DRIVEN SHAFT WITH RESPECT TO THE CRANKPIN OF SAID SECOND CRANK, THE DISTANCE BETWEEN SAID DRIVEN SHAFT AND SAID CRANKPIN OF THE ECCENTRIC LINK BEING LARGER THAN THAT BETWEEN SAID DRIVEN SHAFT AND THE ASSOCIATED CRANKPIN, WHEREBY THE VELOCITY OF SAID RAM WILL BE HIGHER WHILE MOVING FROM SAID FORWARD TO SAID REARWARD DEAD CENTER POSITION AND LOWER WHILE MOVING IN THE OPPOSITE DIRECTION. 